With the growth of computer networks, electronic mail (e-mail) has become a popular means for both personal and professional communication. Due, in large part, to the proliferation of the Internet, e-mail has become a standard means of communication for millions of people.
A sender uses a Mail User Agent (MUA) to create an e-mail message. Examples of MUAs include client-side applications such as Microsoft Outlook and Eudora as well as web-based applications such as Hotmail and Gmail. As is well known, the sender creates the e-mail message by entering one or more e-mail addresses, a message subject, a message body and may also attach files to the message. Each e-mail address comprises two portions. A first portion is referred to as a domain of the e-mail address and references a host name or domain name. The domain is typically located to the right of the ‘@’ sign. A second portion is referred to as a username or account name and is used to identify an e-mail account at the domain. The username is typically located to the left of the ‘@’ sign.
The MUA transmits the e-mail message to the recipient, or recipients, via a transmission e-mail server. The transmission e-mail server includes a Mail Submission Agent (MSA) and a Simple Mail Transfer Protocol (SMTP) server. The MSA contacts a Domain Name Server (DNS) to resolve the domain name of the e-mail address and obtain a corresponding Internet Protocol (IP) address. The SMTP server uses the obtained IP address to transmit the message to a receiving e-mail server for the recipient.
The receiving e-mail server typically includes a Mail Transport Agent (MTA), a local delivery agent, local file storage, and a Post Office Protocol (POP) and/or Internet Message Access Protocol (IMAP) server to allow e-mail message retrieval. The recipient uses a MUA to retrieve the e-mail message from the receiving e-mail server.
In a typical ASCII environment all of the services provided by the receiving e-mail server communicate with a local password file for local username information. The local password file is used for account recognition and authentication.
However, e-mail addresses in the future will potentially contain foreign language (non-ASCII) characters. For example, Internationalized Domain Names (IDNs) are defined as Internet domain names that can potentially include non-ASCII characters. It is envisaged that international e-mail addresses may also include IDN usernames as part of such an e-mail address. Therefore, it is possible that the IDN usernames may also include non-ASCII characters.
These characters are not typically supported by the operating systems on computer servers for usernames, file names, and directory names. In an non-ASCII environment, password files cannot be used due to lack of Unicode character support. In addition most file systems restrict file and directory names to a seven bit ASCII character.
Accordingly, it will be appreciated that there is a need to provide MTAs capable of supporting non-ASCII e-mail usernames.